A suicide attack on a former Iraqi lawmaker's house killed at least six tribal militiamen and wounded seven others in a northern Sunni Muslim village early on Wednesday, police said.

No group has claimed responsibility for the attack but Islamic State militants operate in the area.

A militant wearing a suicide vest blew himself up just after midnight at Adnan al-Ganam's house in the village of Asdira, Colonel Khalil al-Sahn, the police chief of surrounding Shirqat district, told Reuters.

Those killed were members of the Tribal Mobilisation Forces, a network of Sunni militias that back the government in its fight against Islamic State, he said.

The village is north of Tikrit, the capital of Iraq's Salahuddin province.

Islamic State, which had seized control of much of northern Iraq in 2014, lost Shirqat to US-backed Iraqi security forces supported by Sunni tribal fighters in 2016.

A small number of militants are still operating in the area and are capable of launching sporadic attacks, security officials say.

Iraq declared victory over Islamic State in December but security officials say the militants are likely to wage an insurgency after their self-proclaimed caliphate collapsed and they were dislodged from all the territory they held.

Its fighters have kept up a campaign of kidnap and killing, mainly in the provinces of Kirkuk, Diyala and Salahuddin.

A US service member was killed and several other troops injured when their helicopter crashed during anti-militant operations in Iraq, officials said Monday.

The crash appeared to have been accidental, as there were no indications it was caused by hostile fire, Pentagon spokesman Colonel Rob Manning said.